Question

How do you use NSCoding to code (and decode) an array of of ten values of primitive type int? Encode each integer individually (in a for-loop). But what if my array held one million integers? Is there a more satisfying alternative to using a for-loop here?

Edit (after first answer): And decode? (@Justin: I’ll then tick your answer.)

Answer 1

If performance is your concern here: CFData/NSData is NSCoding compliant, so just wrap your serialized representation of the array as NSCFData.

edit to detail encoding/decoding:

your array of ints will need to to be converted to a common endian format (depending on the machine’s endianness) – e.g. always store it as little or big endian. during encoding, convert it to an array of integers in the specified endianness, which is passed to the NSData object. then pass the NSData representation to the NSCoder instance. at decode, you’ll receive an NSData object for the key, you conditionally convert it to the native endianness of the machine when decoding it. one set of byte swapping routines available for OS X and iOS begin with OSSwap*.

alternatively, see -[NSCoder encodeBytes:voidPtr length:numBytes forKey:key]. this routine also requires the client to swap endianness.